[ img - tumi2.gif ]Hotel in Lima
[ img - inca-sol.png ]Quechua
#5 Fifth Edition:
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Inca's balsa log raft

Theory for Daggerboard navigation

How the Guara-steering works is still today something of a mystery

Guaras are a steer system and not a keel supplement

The "keel" of a raft is the long and straight side-trunk, as give the necesary HIGH LATERAL hydraulic resistance in combination with a LOW FORWARD resistance given by the bow

First encounter with balsa rafts

When the spaniards meet the Inca balsa rafts, they were surprised by the cargo they were able to carry - but too the fact, that those rafts were navigated without a rudder, but nevertheless were able to go as close or better to the wind than the Spanish ships. But how that technology worked is still today something of a mystery.

Guaras work only in the combination of wind and sea
[ img - balsa-Bruning.jpg ] [ img - balsas107a-Bruning.jpg ]
Two GLASS PLATE photos - showing some of the LAST balsas
- in the end of 19th century -
courtesy Brüning Museum, Lambayeque

A balsa raft = a Kon-tiki-raft is a raft of balsa-wood-logs with Guaras plunged-in (inserted) between the logs to control that leeway, as every sail-craft has. Guara they called it and Guara is the accepted word for those daggerboards, centerboards, lee-boards, lifting keels, swinging swords - words as all are synonyms for nearly the same - retractable keels. The word Guara is not a Quechua word - seems to come from a language nearer to Equator.

This Guara-system has worked in hundreds of years, even if Thor Heyerdahl had to rediscover it.
Opposite the classic stern rudder as need streaming water to change direction of a boat - a Guara-raft can turn statically = on the site. It need only water and wind.

A first Guara explication

[ img - Ulloa-drawing 1748.jpg ]
Balsa drawing from book of Ulloa 1748

The earliest technical description of the function of Guaras is given by the Spanish scientifics Jorge Juan and Antonio Ulloa as in 1736 were joining a French geodesic mission to west coast of South America.
The original Spanish version of their book is from 1748, can be found in Volumen I  page 314-320
The digital extracts presented here are from the later English edition of 1772:  page 181-183
Inside this English 500 pages book the pages 183, 184 and 185 are giving an exact explication of the function of Guaras.
With the later Guara-troubles in mind it is rather interesting to read this early explication, observing that this knowledge could have saved many 20-century raft skippers from serious troubles.

voyage-frontpage.jpg voyage-183.jpg voyage-184.jpg voyage-185.jpg
pages from book of 1772 - highlighting the text about the Guaras
Transcript of page 182-183:
"Hitherto we have only mentioned the construction and the uses they are applied to; but the greatest singularity of this floating vehicle is, that it sails, tacks, and works as well in contrary winds, as ships with a keel, and makes very little lee-way. This advantage it derives from another method of steering than by a rudder; namely by some boards, three or four yards in length, and half a yard in breadth, called Guaras, which are placed vertically, both in the head and stern between the main beams, and by thrusting some of these deep in the water, and raising others, they bear away, luff up, tack, lay to, and perform all the other motions of a regular ship; an invention hitherto unknown to the more intelligent nations of Europe, and of which even the indians know only the mechanism, their uncultivated minds having never examined into the rationale of it."
- - - -
Transcript of page 183-184:
"Whence it follows, that a Guara being throwed down in the fore-part of the vessel must make her luff up; and by taking it out, she will bear away or fall off.
Likewise on a Guara's being throwed down at the stern, she will bear away and by taking it out of the water, the Balza will luff, or keep nearer to the wind.
Such is the method used by the indians in steering the Balzas, and sometimes they use five or six Guaras, to prevent the Balza from making lee-way, it being evident, that the more they are under water, the greater resistance the side of the vessel meets with; the Guaras performing the office of lee boards, used in small vessels.
The method of steering by these Guaras is so easy and simple, that when once the Balza is put in her proper course, one only is made use of, raising or lowering it as accidents require, and thus the Balza is always kept in her intended direktion."

The arrogant attitude expressed against the indians and their culture could be personal, it could be a common expression of an European culture regarding the indians as subhumans at their service - or it could be deeply ironical against themself. The truth we see today, is that only few of the Europeans have understood the Guara-explication, and that a man as Thor Heyerdahl needed to rediscover the phenomenon, even if he could have learned it in Guayaquil.

Thor Heyerdahl's investigation

When Thor Heyerdahl in his famous sailing lifted up a Guara for repair, he experienced that the raft changed direction. Without intentions, he changed the underwater hull. This discovery caused a subsequent research. Thor Heyerdahl's explication is drawn up after consulting and experiments in the Balsa Raft Society in Guayaquil in Equador, and he furthermore refer to publications of explorers as Humboldt in 1810 and Stevenson in 1825.
cite: "In 1953, Emilio Estrada of Guayaquil arranged for a small test raft to be constructed like the Kon-tiki, of nine balsa logs lashed together and covered by a bamboo deck. Likewise, for navigation, a square sail was hoisted on its usual bi-pod mast in native fashion, and similarly six Guaras were inserted between the logs, two in the extreme bow and two in the stern. No paddles, rudder or steering-oar were carried on the raft, which was launched from the open coast of playas, Ecuador, with a crew of four."
(ref. book: Kon-tiki, p.109).

With 12 sketches as cartoon-strip is demonstrated how a raft, equipped with square sail and Guaras mounted along the main trunk, will react on its Guaras under a static turn all the clock around.

Explication for the strip of sketches
If we want to change course, we have to lift out a Guara in that end, we want to go leeward.
Without hold in water this end will float away with the wind, while the rest of the Guaras will keep their hold in the water.

[ img - thor-Guaras.jpg ]

And that was what Antonio olloa and Jorge Juan had explained 200 years earlier

Balanced side-sliding with a dinghy:

The experiment in Guayaquil was followed up in Denmark, where a common sail dinghy was equipped with two in-line Guaras /centerboards.
Cite from the book: "sejlads på en anden måde"
"The new principle - the use of two 'swinging swords' - makes it possible to alter the pressure of the water from fore to aft under sailing. In other words to steer in this way, and when the vessel is put on course, maintain the course by equalizing the pressure of the water on the fore and aft of the vessel. The new construction works traditionally, so far that vessel and keel skeg works as they have always done."

[ img - YDS-dinghy.gif ]
bow-centerboard   +   a fixed keel   +   aft-centerboard
"As soon as the wind fills the sail, and the aft fin is lifted, the fore fin accordingly will be a falling center for the swinging of the stern until it stands up against the wind.
Contrary - if the aft fin is down, and the fore fin is lifted, the stern will swing into lee, and the wind will blow into the aft.
At any moment and from any position, the swinging can be brought at bay. in other words, the presure of the wind at the sail and the presure of the water on the hull and the keel can be balanced."

research and test by Y.D.Stenild in Denmark 1986:
Sejlads på en anden måde: ISBN 8774661159
[ img - anden-maade4.gif]

Balanced side-sliding with a Catamaran

photo of Dirch with his DIPPING steer paddle, sailing his catamaran on the Carnon River in Cornwall..  > > > 
[ img - dirch.jpg ]

Some pacific double canoes employ the same principle as the Guara-rafts - they are using a handheld paddle for steering.
as Dirch explain: he is NOT TWISTING the steer oar, as they do on the Viking ships, the pacific sailors are holding their paddle on leeward side of one of the hulls, lowering or lifting it to BALANCE THE SIDE-SLIDING of aft-end in relation to for.
The paddle itself keep to the boat pressed by water - just as every lee-bord does.

please note:
This last example indicate, that it is the AFT Guara as is important. With the aft you can controll the pointing.
Under normal sailing ahead, the bow is pressed into the sea and therefor hindred in side-sliding. Why fore-end don't need any Guara, except for static turn.

That no Guaras needed in extreme for, seems in conformity with the old drawing of admiral Paris 1841

The four observations - respectively with two rafts, a dinghy and a catamaran - show the same empirical result:

Jorge Juan and Antonio Ulloa describe this very exactly and too show us a drawing of a indigeneous raft.

Emilio Estrada placed his six Guaras as pairs along the central log, and when lifting up a Guara /centerboard for or aft, that end of his craft lost its hold in water and slided sidewards with the wind. Technically he was changing the shape of the underwater-hull and moved the turn-center of his raft to a new position, after what the raft made a static turn.

Stenild in the same way balanced a dinghy - extending the natural keel with a centerboard for, and one more aft - and then throw away the rudder.
Lifting or lowering the Guaras (in the centerboard-version) in bow and stern - the side-sliding was balanced.

Dirch with his handheld paddle confirm the phenomenon, employing the same principle - balancing the side-sliding (without need to twist the paddle).

Guara steer system in Asia

under our way through an ocean of information, we have discovered that Guaras /daggerboard steering too is known in both the island of Taiwan and in area of Vietnam for use on their bamboo- rafts - and both claim to have got the daggerbord-steering from China.
   ref-1:   Cheng Kung University: A brief history of the Evolution of Taiwanese Rafts
   ref-2:   UNESCO:
Asian shipbuilding technology
The only reason why this papers are known by us is, that the author too has written in English language.
In none of the asian cases we have been able to decipher anything more around asian Guara-lore.
This references to Asian rafts we have got from the book of P.J.Capelotti: Sea Drift.
[ img - seagoingChineseRafts04.jpg ] [ img - Taiwanese-raft-model.jpg ] [ img - Taiwanese-draft.gif ]
Inevitable such information bring us to ponder over, if there had been Chinese contact across the Pacific Ocean prior to the famous admiral Zheng He who 1421 "discovered the world". We expect that china still keep information as not has been translated and published in the western hemisphere around their admirals voyage then.

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The empirical theory of BALANCED side-sliding

We can make our raft point where we want by dipping the Guaras in AFT in balance with those FOR
= We are controlling the leeway of both ends independently

Balance of side-sliding is a theory as seems serviceable in all cases and for every floating sail vessel - rafts as well as boats, monohulls and multihulls.
The four reports all explain, that on a vessel sailing with the wind comming in over the side (beam - broad or close reach), we can balance the leeway of bow and stern independtly, by setting down Guaras.
Balancing the sidesliding between for and aft end is the way to control the pointing of our vessel.

Animation of a static turn - with wind abeam
[ img - balsaturn.png + balsaturn.gif ]
If we lift the front Guaras, the wind will press on the vessel and slide the bow sideways, while the raft or the dinghy is pivoting around the submerged aft Guaras as a hinge
- the craft will turn until the stern is pointing against the wind. Then the craft is ready to hoist sail and sail off.
Otherwise, if we lift up the aft Guaras /daggerboard /centerboard, the stern will side-slide and the craft (here the dinghy) will now turn up her bow against the wind.

[ img - dinghy.png + dinghy.gif ]

Of same reasons why a rudder is placed aft on the hull, the aft Guaras are the most useful for steering a raft, the bow is kept fixed by the bow-wave.
Lifting the aft fin (Guara) the stern will give more leeway and slide away = the boat will luff up.
Lowering the same aft fin will give us less sidesliding and our craft will bear away.

The balanced sidesliding is the reason why the first observations 4-500 years ago of the manoeuvrability of balsa rafts all told us, that these South American balsa rafts were able to sail out in the morning and return to same site on the coast in the evening (what not always was possible for the European vessels). But how that steer-system worked, was not analyzed.

What the old croniclers neither told us was, that a balsa raft steered by Guaras in-line could have some difficulties running for the wind, if not plunging down suficient AFT Guaras.
But that problem we know from our monohulls, that by running we must let the sail draw and not push against the hull. That theme we will treat in a separate chapter. running for the wind

Examples of similar physic balances:

[ img - 3-forces-k.gif ]
A balanced sidegliding isn't something special for South American rafts. We can see the same constalation balance of 3 forces on a schooner or an eel-drifter, where we can influence on the sail direction by adjusting the wind-press between main and mizzen.

There are hard-core sailors as declare, that they can sail their boat without a rudder - by 'playing' with their sails only.

[ img - 3-forces-s.gif ]
[ img - seesaw-2.gif ]
On a steelyard scale we can tilt the lever as we will, by changing the load or move the load along.
That is a balance between 3 forces on same line.
And that is what we are doing on our craft.
[ img - steelyard.gif ]
Of course we know, that the expression 'IN-LINE' not is correct: A scale is supported a little bit over the lever arm - and the ce-center of a sail is a little to leeward side of the center line of the vessel, whereas the clr a little to windward of a heeled sail craft.
- and that is exactly what make the things work.

A working method employing
balanced side-sliding

[ img - eel-drifter.jpg ]
An eel-drifter
is a flat-bottomed fisher boat, as work drifting sideways, hauling a drag-net along the sea bottom.
Having more masts and sails, the trick is to control their drift balancing by their sails - as indicated earlier.

The same way of fishing: hauling a trawl along the bottom while drifting slowly sidewarts was too used in the shallow lagoons along the southern shore of the Baltic sea.


CONCLUSION of balanced side-sliding:

A Guara steer-system work only with the combination of wind on sails against the hydraulic resistance of underwaterbody

By use of your bow and stern Guaras, you can dominate the pointing of your vessel
- and if your sail (or sails) is adjusted for that pointing, you will sail -

[ img - weathercock.gif ]

The WEATHERCOCK principle

[ img - slant-picture.png ]
as well as you can hang a picture slant, you can point your boat !
You decide the hanging point - or where the hold in the water shall be !

[ img - CLR5-star-33.gif ]
The common center of the Guaras make the hold in water
Weathercock raft with only four Guaras:
A raft with sail is out of control, until we plunge down a Guara/daggerboard
and here we will show what what a NORTHERN wind will do, if we plunge-down into the outermost cracks between trunks.

#1):       with Guaras plunget in both aft corners and a northern wind blowing - the raft will react and pivot around the blue-star-marked point between the two Guaras while mast and sail drift leeward - ready to take off running with course against South.
#1):[ img - raftS2.png ]
#2):[ img - raftE2.png ]
#2):       If we plunge in port Guaras both for and aft, the raft again will pivot around its new point between the two daggerboards and sail/mast go leeward - subsequent the raft will point against East with wind abeam on port side.
#3):[ img - raftNW1.png ]
#4):[ img - raftNW3.png ]
#5):[ img - raftNW.png ]
[ img - pahi63.gif ]
A side leap to Guara steering on oceangoing Catamarans:

#3, #4 and #5 show that with a Northern wind we wil have similar options for a Nord Western pointing. A Guara give hold in water, but is too a waterbrake for headway.
What is best for actual raft in actuel situation skipper must find out.
[ img - raftstars.png ]

#6):       If we study the symmetry in our four Guara slots, the above examples show us, that we without greater problems can move or create pivot point all the way around the mast and all over the raft, as demonstrated by stars.
And still more Pivot points are possible, if some of the Guaras only are PLUNGED IN PARTIAL.

After setting the Guaras, the raft get hold in water and will turn just like a weather-cock around its pivot point ready to go ahead on a new course.

A conclusion:
You can control the pointing of our raft all the compass around - with your Guaras alone
- and you are not limited to use Guaras along center-trunk -

A modern explication of
what the old South Americans did

[ img - balsa1841+.jpg ]
Guayaquil, Ecuador 1841
The drawing was made by the french lieutenant, later admiral François-Edmond Pâris
is our technical most detailled of old sketches, and seen in the light of his later career we feel no reason to doubt of its reliability

With reference to this old french drawing from 1841, we with three simple sketches can demonstrate, that what they did on a raft was to move the center of hydraulic resistance between for and aft.
That has as consequence, that the vessel will react as the rule says: the wind will blow and our craft will turn, until the centre of wind is directly downwind from the actual pivot-centre, defined by the position of the Guaras - and we have got a new pointing.

[ img - CLR5-star-33.gif ]
The hold in water is often called CLR = Center of Lateral Resistance

[ img - Guaras-FF.gif ] [ img - Guaras-AF.gif ] [ img - Guaras-AA.gif ]

In both the raft and the dinghy case named before, we were manipulating = changing the shape of the underwater body and in this way we controlled the position of Center of Hydraulic Resistance - and with that the pointing of the vessel.

Nevertheless, the old French drawing give us more information. There are reasons to note the place of formost Guara-group is just in front of mast and not in the bow. That is a place as seems placed just under where the sail center CE can be moved in its half circle.

[ img - CE4star-37.gif ]
The CE = Center of Winds Effort is on a square sail the center of the canvas
[ img - semic.png ] [ img - semicircle1841.jpg ]
The semicircle of CE = Center of Effort
for a lonely square sail indicated on the old drawing

that place has as consequence that the Guaras front of mast not will contribute much to the pointing of the raft - they are to consider more as a keel-arrangement. On the other hand, the need for front Guaras to steer isn't great; while a sailing ahead, the raft will press her bow into the sea and side-sliding of bow will be hindered.
It is the aft Guaras as have the job to point the raft.

The common rule for any sail-vessel:
The wind will blow the vessel leeward of her hold in water!
and thus define the pointing of the craft
- and that is what the greek deities Zephyr and Poseidon together try to explain here:
[ img - anden-maade-D.gif ] [ img - anden-maade-A.gif ] [ img - anden-maade-B.gif ] [ img - anden-maade-C.gif ]
Seen in a cross view with wind abeam, it is easier to accept, that the Centre of Wind for sail /mast is clearly blown leeward of the Centre of Hydraulic Resistance of the hull.
- and behold, a boat will heel the centre of wind more out, but a wide-beamed raft don't need to heel - and neither does.

sail dinghy with wind abeam
[ img - CE+CLR+dinghy.gif ]
viking replica Kraka
[ img - CE+CLR+kraka.jpg ]
raft with her Guaras
[ img - CE+CLR+raft.gif ]

- but seeing the last rightmost picture of a raft, we could ask, what will happen if instead along the central trunk, the Guaras was trusted down in the outmost luff position ?
- and the answer is, that the "weathercock" will stay more stable.

[ img - weathercock.gif]
this is why we call it the "Weathercock Principle":
the weathercock will always point against the wind

NOTE two things:
A): That is right, that more Guaras plunged in give more keel and theoretically less leeway - if you need that,
- but more Guaras down too give a loss in headway. Therefor, if you can sail alone with your long straight side-trunk as keel and few Guaras down - then do that.

B): Large distance from pivot point of weathercock to its centre of wind, do the same as large distance from the Hydraulic Centre of the Guaras to the centre of sails - that bring less swing, less oscillation of the weather-cock and less oscillation of the raft when gusts come.

The rules for "rudderless sailing" is valid too for rafts

[ img - Rudderless_Sailing_by_Joel_Brand.gif
A rudderless sailor tilting his centerboard to move his hydraulic center more aft.

A raft is sailing "rudderless" - simply because she has no rudder - and the principles of "rudderless sailing" is a theme for much writing of books, manuals and at internet.
Link to some rudderless sailing.

The hull of the raft itself skipper has to accept with its strong and weak build-in qualities - but he can operate his Guaras and adjust the sail

The center of water resistance will under all the sailing be in balance with the forces from wind - in every moment. This balance is what define the pointing of the craft, which too means, that the only way skipper has to correct the pointing of his Guara-raft is by changing the underwater-body = adjusting the Guaras - or move the center of sails, if rigging permit that.

The dynamic forces from wind and from water play together

Sailing along the dynamic forces move the hydraulic center forward, and with the increasing forward speed, we have to adjust Guaras. On the other hand, any sail sheeted out for sailing too move its center forward (and to lee), and as long as the dynamic forces move both wind- and hydraulic centre forward, those two movements will keep in certain balance, and things seems fine, but nevertheless Guaras have to be adjusted.

The dynamic part of both water and wind will oscillate with gust and waves and that make exact calculations of center of wind and center of water resistance impossible with any degree of accuracy.
But we neither need to know that - we only need to know their nature to be able to counteract the actual situation by adjustments of sail and Guaras.

With the two theories at hand: #1): balanced side-sliding - and #2): the weathercock-principle, skipper know something about how his raft will react, when he plunge-in or lift-up a Guara or two somewhere on his raft, and that is what skipper has to do.

The task of a prow is to stabilize the sailing by cleve and split up the in-comming flow of water in two - going left and right - passing port and starboard sides.
If the shape of the stem make the CLR move too much forward - more than you can adapt with your actual sail setting - you can get in troubles, running the risk that the raft will luff too much up, so the sail get into the dead area of no-go-zone, and therefor can't work. The no-go-zone is for classic square sailers rather broad.   [ sad example here ]

[ img - Points-of-Square-Sailing.png ]
the broad no-go-zone is characteristic for square sail rigging

Sailing on, your sailing depend of how your sail will transform the wind force into a forward force and a broadside force, and the propagation in those two directions will depend of that hydraulic resistance, as the vessel meet in the two directions, and respectively define the headway and the leeway.

Small tips for new raft sailors:

Do as the old investigations indicate: plunge in a pair of Guaras in front end, and a pair more in aft end - and use those two most extreme pairs for steering.
If your raft is well trimmed - that will do it.

Any fin plunged down under a craft will of course reduce leeway, but too reduce headway. It is astonishing how much a surplus of long and deep Guaras can brake the headway.
Even if a Guara in some situations is to consider as a fin or a keel-supplement, too many Guaras plunged down too near stem and stern too will reduce the impact from your steer-Guaras, reducing their influence on the common center of hydraulic resistance.
In all cases that will be the Guaras most distant as will influence most on the shape of underwater body, and therefore those as you will use for steering. Probably the aft.

But if you absolutely want more keel to beat higher to the wind or something like that, then you could add a lee-board, a centerboard or a luffboard by plunging in the steer-neutral midship zone. That means in the outer rim, where you have access. First a luff-board in wind-side more than in lee-side because of a useful stabilizing wind-vane-effect, but if you want still more keel - then too in center and lee-side - but always steer neutral - in a belt just in front of mast.

Hypothesis - as still miss empirical evidence
Too many Guaras plunged in as keel-supplement will be a hindrance for steering

Preparation before sailing out:
[ img - distrib.Gu.png ]
a proposal for distribution of Guara-holders: - but not for the Guaras themself.
- in extreme aft for steering - and in bow for trim and static turn
- "just for the case" midship, as keel supplement in situations you may need it on your way over the ocean

One thing is Guara-slots, but don't fill up your raft-bottom with Guaras !
Note the observation from Dirch: when sailing ahead, only aft Guaras or dipping paddle is needed for steering. Ref:
Tangaroa 1965 passed the dangerous Tuamotu Archipelago of French Polynesia by employing 3 Guaras only. One in front - and two aft.

the crowded beneath of the Manteño raft 1996
[ img - manteno3.jpg ]
they happend to break around 10 Guaras
[ img - Tangaroa2-guaras.jpg ]
underneath Tangaroa2-2006

the raft-rule is still:
Guaras is a steer system and not a keel supplement

- the "keel" of a raft is the long and straight side-trunk, as give the necesary high lateral hydraulic resistance as play together with a low forward resistance given by the bow

The short instruction for raft skippers:

[ img - howTo2.png ] [ img - howTo3.png ] [ img - howTo4.png ] [ img - howTo5.png ]

The steps to get sailing:

0): A raft with no Guaras plunged-in is out of control. As soon as the first Guara is thrusted down the raft will get hold in water, whereupon the centre of wind's attack will blow leeward

1): Hoist and set the sail for the course you are planning and when tack and sheet fastened - then estimate where the centre of wind will be

2): Plunge in some Guaras as shall have their center of water resistance (the pivot-point) somewhere upwind the wind-center

3): When sailing, adjust the Guaras and sail. The dynamic streaming of wind and water elements will change and move both the centre of wind and the centre of water resistance to a position more ahead and a little to lee, but still: centre of wind will blow leeward of the centre of water resistance and define the pointing.

4): Sailing-on, skipper only have to adjust the Guaras for the dynamic forces on sail and raft to keep the pointing.
Fore Guaras lifted up, because the bow and its wave take over - and probably more Guaras plunged down aft.

- before you enter an ocean raid - gain self-confidence, security and safety -
learn your own raft:
take a test-trip around the nearest island

post scriptum:

if you are in doubt what the mentioned centres CE and CLR really stand for - then ask a wind-surfer  
[ img - ce+clr.gif ]

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Lima - yule 2017